It is fairly common practice to provide automotive vehicles with electrical systems which can operate door locks and other components, including antitheft systems, utilizing a remote unit which can be actuated by the operator and may, for example, be provided with a key which can operate an electrical switch or a mechanical lock or both.
In such electrical control systems for a vehicle, a control unit is provided which may be connected by appropriate lines with the electrically actuatable motor driver for the mechanical components of the or each electrically operated door lock and optionally with other vehicle components.
The control unit itself may be associated with actuators fixed on the vehicle, e.g. push button switches, which may be utilized to operate the door locks and such other components like the window lifters, locks for various vehicle compartments and even accessories such as electrically operates seats, memory and the like. The unit may in addition respond to a remote actuator, an actuator which can transmit signals to the vehicle in a wireless manner, i.e. by radiowaves, ultrasonics or infrared waves.
In general, such a control unit is supplied with electrical energy from the starter battery of the vehicle and the vehicle may be equipped with an emergency switchover device cooperating with an emergency energy source which, upon failure of the starter battery because it is damaged, missing or insufficiently charged, enables at least one of the vehicle door locks to be operated.
The individual door locks can be provided with electrical servomotors or stepping motors or motors with step down gearing which are operatively connected to the wheels, segments, levers or the like making up the mechanical parts of the lock. In addition, each lock will normally have a motor driver which is energized via the control unit and which, in turn, applies the appropriate signals for operating the lock motor. The term "motor driver" as here used applies to the motor itself, the motor in connection with any step-down gearing which may be required, and any electronic circuitry required in association with the particular motor. The emergency circuitry can include at least one measuring circuit network which can measure the voltage of the starter battery and switchover to the emergency power source when a voltage is detected by this sensor which is below a normal starter battery voltage and threatens to be incapable of operating the electrical units of the system. Instead of a discrete emergency circuit, the emergency operations can be effected by a program of the vehicle computer which can respond to a diminution of the starter battery voltage below a certain threshold. In other words the emergency circuitry becomes effective upon the development of an undervoltage, namely, a voltage at the starting battery below which control functions of the control unit cannot be reliably effected. A typical undervoltage at which such emergency source operation is triggered may be, in the case of a normal 12 volt vehicle battery system, say 11.4 volts.
It will be understood that the emergency functions which have been described should be effected not only in the case of an effectively discharged battery but also in the case of electrical separation of the starter battery from the vehicle, i.e. upon theft of the starter battery or its removal for other reasons. In the case of a starter battery separated from the vehicle the voltage measurement circuit registers a fictitious voltage of 0 volts. Systems of the aforedescribed type are available in a variety of configurations. For example, in one such system as described in German Patent Document DE 19 530 721 A1 (corresponding to U.S. patent application Ser. No. 08/661,485, filed Jun. 11, 1996, U.S. Pat. No. 5,736,793 of Apr. 7, 1998 a single emergency battery and a central emergency circuit is provided. The device is so arranged that, upon the development of the aforementioned undervoltage, the emergency circuitry will decouple the control unit from the starter battery and connect the emergency battery to the control unit.
The electrically operated components of the vehicle as described in this patent document include, so-called basic components and so-called comfort components. The basic components include the vehicle door locks and usually also the antitheft system. Comfort components can include those which need not be operated when there is insufficient power available, for example window lifters, compartment heating or cooling and the like.
Upon the development of an emergency situation, calling for use of the emergency power source, in general, the comfort components are deactivated so that the energy of the emergency source can satisfy the need for operation of the basic components as long as possible. The emergency energy source can be a battery, e.g. a so-called primary battery, an accumulator or storage or secondary battery, or even a condenser or capacitators. The emergency energy supply is thus fixed and dimensioned to supply the basic vehicle components with electrical energy upon the discharge of the starter battery or some other act which may render it incapable of functioning. The emergency battery can be provided in the interior of the vehicle or even in the trunk or luggage compartment, i.e. in a more secure location than the starter battery which normally is found in the engine compartment. The emergency energy source, when located in the interior of the vehicle thus is better protected in the case of a crash and has a higher probability of being undamaged so that it can be a source of energy for the lock when the latter must be actuated from the exterior of the vehicle by a remote operator in the case of such a crash or when the vehicle must be opened from the exterior upon failure of the starter battery.
EP 0 694 665 A1 describes another control system wherein the emergency system is subdivided into a multiplicity of emergency units, each of which can have an emergency circuit and an emergency energy source. The individual emergency units may be associated with respective vehicle door locks and can even be built into the corresponding vehicle door or vehicle door lock. This increases the reliability of the emergency system in the case of a crash since it is highly probable that at least one vehicle door lock will be unaffected in the event of such a crash. Put otherwise, it is highly improbale, in the case of a crash, that all of the door locks will be adversely affected and hence that the emergency source and circuit of every lock will be unavailable to enable the opening of the door.
In this system, however, the emergency energy source must be equipped to receive charge from a generator or alternator of the vehicle or the starter battery with a voltage which can range from 9-20 volts and, as a consequence, the emergency energy source must be relatively bulky and must work with comparatively large units, such as motor drivers which are dimensioned to operate at the high voltages. It is a problem to build such units and the bulky sources required for emergency purposes into vehicle door locks.